In a full system solution, physical or virtual computers running applications are referred to as masters, and are protected by a virtual machine replica inside a virtual machine platform. The virtual machine replica can take over should the master be unavailable. Each volume of data on each master is protected by a virtual hard disk. If a disk drive on the master has two volumes, two virtual disks are created for the replica.
When a master is unavailable, such as via a breakdown, the virtual machine platform will create a virtual machine replica and attach the virtual hard disks to the virtual machine replica. Many virtual machine platforms are limited in the number of virtual disk drives that can be handled. Delay may also be encountered when switching over to the virtual machine replica, as the replica must be created. In addition, virtual platform resources and performance may be burdened with other virtual machines.